[petsc-dev] DM RefineLevel and CoarsenLevel

[Matthew Knepley]

On Sun, May 6, 2012 at 5:57 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:

> Now the next round:
>
> For semi-coarsening, we used to have stuff like -da_refine_hierarchy_x
> 1,1,3 -da_refine_hierarchy_y 2,2,1 -da_refine_hierarchy_z 2,2,1. Two
> changes make this harder now:
>
> 1. You essentially got rid of DMRefineHierarchy (it's not called any
> more), so each call to DMRefine and DMCoarsen have to figure out where they
> are.
>

This is a huge mistake. The only way unstructured stuff works is through
this interface. That is why I added it

   Matt


> 2. Since the coarse DMs are not reused by PCMG, but instead created again
> using DMCoarsen, we have to figure out how to reverse the refinement
> process so that the same coarse grids get reconstructed again.
>
> I added a DMRefineHook so that we can port data the other way and I
> modified DMCoarsen_DA and DMRefine_DA to not call DMDACreate{1,2,3}d
> because it eagerly calls DMSetFromOptions before we can set the
> refinement/coarsen level. Unless someone stops me, I'm also going to add
> coarsen_{x,y,z} fields to DM_DA because the refinement ratio may have
> nothing to do with the coarsening ratio.
>
> I have no idea how to expose semi-coarsening through a C API other than to
> hold the refinement/coarsening path arrays in each DM_DA so that
> refinement/coarsening steps can be retraced.
>
> On Sun, May 6, 2012 at 1:57 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
>>
>>  Fine
>>
>> On May 6, 2012, at 2:44 PM, Jed Brown wrote:
>>
>> > Should the refinement level be copied over by DMCoarsen (and the
>> coarsen level be copied by DMRefine)?
>> >
>> > It's useful for diagnostics to be able to define a universal level. If
>> I use PCMG and -snes_grid_sequence, there is effectively a sequence like
>> >
>> > DMCreate(,&dm0); // r=0,c=0
>> > DMRefine(dm0,&dmf); // r=1,c=0
>> > DMCoarsen(dmf,&dmc); // r=0,c=1
>> >
>> >
>> > I would like a way to identify dmc as being on the "same level" as dm0.
>>
>>
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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